The present invention is directed to a knife for cutting fibrous insulation batts. Cutting this type of material is a very difficult and awkward task even for professional installers of the material. The material can be cut with a large pair of scissors but this procedure is very time consuming. The conventional utility knife is usually the cutting tool of choice by most professionals. Due to the looseness and compressibility of the material, several passes of the knife are usually required to cut the material. An elongated straight-edged tool is usually used to compress the fiber sheet of material and to guide the knife along a predetermined line of cutting. However, even this procedure is less than satisfactory. Care must be used to avoid hitting the guide edge of the compressing tool with the blade of the utility knife which increases the cutting time. Although the fibrous material is compressed along the guide edge of the compressing tool, the fibrous material extends upwardly, abruptly from the guide edge of the compressing tool, thereby making it difficult to cut the fibrous material. Also, since the operator has one hand on the compressing tool and one hand on the utility knife, he or she is unable to grasp the portion of the fibrous material which is being cut off and to prevent it from being dragged forwardly by the knife and interfering with the execution of a smooth, clean cut.
Previous devices have attempted to cure some of these difficulties by incorporating a standard utility knife in a frame which compresses the insulation batt. These devices have been less than satisfactory for a number of reasons.
First, the cost of manufacture was relatively high, because several component parts and assembly operations are required to form a complete assembly. Second, the knife housing was apt to wobble or become loose, or the knife itself may wobble or become loose within the housing. This may result in an uneven cut and may also endanger the operator's hand.
Furthermore, these devices tended to be somewhat fragile because of the presence of moving parts.
Also, these devices required the retrofit of another device: the utility knife, and were not built as one complete unit, ready to use without assembly.
In addition, the positioning of the operator's hand in previous devices did not give the operator a comfortable grip, prevented him from seeing the cut as it was being made, or exposed the operator's hand to contact with the insulation batt resulting in skin irritation.
Earlier devices which incorporated utility knives also had the utility knife's problem of tearing the insulation batt because the cutting action was concentrated at a point or along the length of a short blade.
Also, the use of utility knives requires the blade to be replaced when dull, which can be expensive and time consuming.
In such earlier devices, the compressing frame tended to contact the insulation batt over a relatively wide area causing unnecessary drag and friction and also dispersing the compressing force over an unnecessarily wide area, resulting in additional expenditure of energy to make the cut.
Furthermore, such earlier devices could not cut through multiple insulation batts at once because of the short blade of the utility knife. Often it is desirable to stack insulation batts atop one another and cut several at once, and this could not be accomplished with earlier devices.
The problems with earlier devices are amply illustrated by U.S. Pat. No. 5,075,974, which discloses a cutting tool for use on insulation batts, or other fibrous compressible materials. The tool comprises a utility knife housing having a razor-sharp cutting blade extending from one end thereof. The elongated housing is sealed in a "U"-shaped cradle that is attached to two parallel rods or wires. Flexible straps extend around the cradle and the knife housing to retain the knife housing in a fixed position on the cradle.
The parallel rods terminate in guide rings near the end of the knife housing that carries the cutting blade. The parallel rods are reversely curved to form a spring system that includes wire-like posts extending upwardly through the above-mentioned guide rings. The spring system can be positioned against a batt of insulation to exert a compressing action on the fibrous batt material when a downward manual pressure is exerted on the knife housing. During downward motion of the knife housing, the guide rings slide down on the parallel posts presumably for the purpose of ensuring a true vertical motion of the knife housing. After the insulation batt has been compressed, the knife housing can be drawn across the batt surface so that the razor blade cuts through the compressed batt thickness.
Clearly, the cost of manufacture of such a device is relatively high, because several component parts are required to form a complete assembly.
Further, the flexible straps are relatively close together such that the knife housing is apt to wobble or become loose in the cradle during operation. Also the presence of the straps makes it somewhat difficult for the workman to get his hand around the knife housing. The straps and cradle add to the side-to-side bulk dimension of the tool so that the workman cannot get a firm grip on the knife housing. This leads to the possibility that the hand may slip and contact the razor blade.
This device is also somewhat fragile because of the presence of so many moving parts.
Furthermore, the device requires the retrofit of the utility knife and is not built as one complete unit ready to use without assembly.
Furthermore, the positioning of the operator's hand gripping the utility knife prevents him from seeing the cut as it is being made. This also exposes the operator's hand to contact with the insulation batt resulting in skin irritation.
The small, sharply pointed, razor sharp utility knife of this device also has a tendency to tear the insulation batt rather than cutting it smoothly. The blade must be replaced when dull, adding to expense. The razor sharpness of the blade and its exposed location can easily lead to severe injury to the hand.
Also, the spaced-apart rods of this device contact the insulation batt over a relatively wide area causing unnecessary drag and friction and also dispersing the compressing force over an unnecessarily wide area resulting in additional expenditure of energy to make the cut.
Furthermore, this device is incapable of cutting through multiple insulation batts simultaneously since the short blade can only penetrate one batt without the knife housing interfering with the cut.
U.S. Pat. No. 5,325,594 has fewer problems than the above patent but still has the disadvantages associated with using a utility knife. Also, the wide plastic compressing member again causes unnecessary friction with the batt while dispersing the compressing force over too broad an area. Again, the position of the operator's hand prevents him from seeing the cut as it is made. Also, it is impossible to use this knife to cut multiple batts simultaneously as the knife housing and compressing member would interfere with the cut.
There is a need for an improved knife for cutting insulation batts which overcomes the problems mentioned above.